The present invention relates to a fan for an air-guiding system of an outboard motor, which comprises an internal combustion engine and a covering hood bounding an interior space for the internal combustion engine.
An internal combustion engine known from U.S. Pat. No. 6,302,749 B1 operates as an outboard motor for driving a watercraft. The internal combustion engine is surrounded by a covering hood which bounds an interior space. For ventilation and venting of the interior space, inlet and outlet devices for airflows moving in the interior space of the covering hood and serving to act upon housing surfaces of the internal combustion engine are provided on the covering hood, which substantially covers the internal combustion engine. The internal combustion engine comprises an upright crankshaft, which interacts with a plurality of pistons and drives balance shafts at an upper end region by means of an endless drive. An alternator with an upright axis of rotation projecting beyond an upper side of a housing of the internal combustion engine is provided with a fan, which ventilates and vents the interior space of a hood-like endless drive covering.
German document DE 102 05 109 B4 concerns an outboard motor provided with a vertically oriented crankshaft and a plurality of auxiliary units attached to an outer side of an engine housing of the outboard motor. A covering hood covers the outboard motor and the auxiliary units. Air inlet slots, which interact with an adjacent air-conducting device, are provided on a rear side of the covering hood. The air-conducting device ensures that fresh air is conducted into an upper region and a lower region of the interior space of the covering hood or to the engine housing and to the auxiliary units.
European document EP 2 696 054 A1 relates to an outboard motor, the internal combustion engine of which is clad by a covering hood bounding an interior space. The internal combustion engine has a housing which accommodates two parallel and upright crankshafts of a crankshaft system.
It is the object of the invention to design a fan for an air-guiding system of an outboard motor with an internal combustion engine and a covering hood bounding an interior space, with the fan arranged and effective in the interior space in such a manner that airflows moving in the interior space contribute in a specific manner to cooling of the internal combustion engine. However, it is also to be ensured that precautions suitable for protecting people are taken with regard to the fan and flywheels of a crankshaft system of the internal combustion engine.
The object mentioned is achieved by the features claimed. Further features of the invention are set out in dependent claims.
Advantages primarily achieved with the invention are that the fan influences airflows in the interior space of the covering hood in such a manner that the airflows first flow, via the inlet opening and the first conducting device, into the interior space of the covering hood. These airflows are guided in a specific manner past surfaces of the internal combustion engine and the auxiliary units thereof, and the airflows bring about an operation-ensuring cooling effect of the surfaces within the covering hood. The fan is placed onto the flywheel of the crankshaft of the internal combustion engine, and the fan is carried and taken along by said flywheel, i.e. the functional region of the flywheel is extended, and the fan and the flywheel can be produced as an assembly. The cooling effect is assisted by the fan having an impeller system with a mixed flow, a radial flow, or the like, and by the fan conducting heated airflows via a conducting device and an outlet opening in the covering hood in a defined manner to the outside or into the atmosphere. The design is supported in that, in a center longitudinal axis of the crankshaft comprising the shaft journals, the flywheel has a radial carrying region on which a corresponding support region of the fan wheel rests, so that at least one screw connecting the flywheel and the fan wheel to form a constructional unit is effective. An exemplary design here is that the fan wheel is formed by a cylindrical body and has two ringed carriers, which run at an axial distance with respect to each other and are connected to each other with the interconnection of fan blades. An expedient solution is that the fan wheel is provided with a dome-like air-conducting element for heated air in the region of an axial fastening screw penetrating the carrying region and the supporting region and keeping the flywheel in position on the shaft journal.
When the covering hood is open or removed and the internal combustion engine is running, to permit people carrying out service activities on the outboard motor to act with little risk of injury, the fan wheel and the flywheel are clad with a protective hood which has a cover region with a central inlet opening and a casing region. The protective hood is designed in the manner of a housing, in which the second conducting device for the heated airflows is integrated, and the housing has a tangential portion, which is provided with an outlet device at an end region, with the outlet device connected to an outlet opening in the covering hood. Furthermore, the protective hood on its outer side has one or more stiffening ribs, which make possible the use of lightweight materials, such as composite materials, plastics, or the like.
The invention is optimized by having the outboard motor comprise an internal combustion engine with a crankshaft system having two upright crankshafts, which crankshafts project with shaft journals beyond an upper side of the housing of the internal combustion engine. Flywheels are fastened to the shaft journals, and the flywheels are arranged offset with respect to each other, as viewed in the vertical direction, and mutually overlapping. Scales are set by having the one flywheel with the fan lie above the other flywheel, as viewed in the vertical direction, and the latter flywheel is clad with a connecting protective hood, which supplements the protective hood and has a cylinder portion. By way of example, the protective hood and the connecting protective hood are produced as a fan and flywheel covering produced from a single piece or assembled from a plurality of parts. The fan and flywheel covering is provided on outer regions with fastening eyes at which the fan and flywheel covering is kept in position on the housing of the internal combustion engine with the aid of holding devices which can easily be realized. It is also technically preferably for each holding device to interact with the fan and flywheel covering with the interconnection of an elastic support element.
Finally, it is of high structural and functional importance that the airflows enter via the inlet opening in the first upright hood wall and the first connecting device adjoining the inlet opening into the interior space of the covering hood. The fan is arranged adjacent to a second upright hood wall of the covering hood, which hood wall extends at a distance from the first hood wall, as viewed in the longitudinal direction of the outboard motor, and conveys the airflows over a relatively large region of action, which runs in the longitudinal direction, past the surfaces of the internal combustion engine and the auxiliary units. The fan conveys heated airflows as exhaust air with the aid of the second conducting device into an outlet opening in the covering hood to the outer side of the covering hood or into the atmosphere.